A Tale of Two Chefs: Debt-Free Engineering in the Age of AI — Obie Fernandez | RubyConf Austria 2026

Keynote from RubyConf Austria 2026, recorded live on May 30, 2026 at Das MuTh theatre in Vienna. Obie Fernandez — author of The Rails Way and Patterns of Application Development Using AI, CTO at ZAR — tells the story of two chefs in two very different kitchens, building a fintech together with AI. One chef is Sebastian, ZAR's lead architect: a perfectionist running a Michelin-star kitchen, where almost every line of ZAR Core — a stablecoin wallet serving underbanked populations across a 60+ country roadmap — touches users' money. The other is Obie: idealist, delegator, running three or four Claude Code sessions at once on internal tools, never reading every line, wearing the --dangerously-skip-permissions t-shirt on stage. "I'm a control freak and you're a free spirit." What they share: a total intolerance for technical debt. What differs is when they pay — Sebastian up front, with planning and specifications; Obie afterwards, with cleanup passes he finally has the bandwidth to make. Highlights: • The cautionary tale: kr8d, a vibe-coded fun-employment app that collapsed under its own featureweight • Sebastian's kitchen by the numbers: a single 37,000-line cleanup PR, deleting five lines for every line added — while features keep shipping • Obie's kitchen: five Rails apps, 1000+ commits, 400k+ lines in five months — Nexus, Agentis, Imperium, and Eventis, an event bus that's an active participant in the conversation • The /goal workflow: plan, implement, ship, deploy, verify — then walk to the cafe and supervise from your phone • Compounding: every problem you solve should make the next one cheaper — 75 custom skills, /fresh, /ship, and a skill that writes skills • The two-week Flutter → React Native rewrite the team said would take two months • Why Rails conventions matter more than ever: every shape choice you leave open is an invitation for the model to get non-deterministic • Open source from ZAR: Servus (a disciplined, schema-validated service-object pattern), Amounts (fungible amounts with units and type safety), and Praxis (conceptual linting — RuboCop at the level of intent, not syntax) • The uncomfortable truth about code review in the agent era — and why automated constraints will save us from ourselves "Don't tolerate debt. It's not needed anymore." Chapters 00:00 Introduction 01:35 A story of two chefs 02:26 October 2025: a vibe-coded app collapses under its own weight 05:28 Joining ZAR and meeting Sebastian 08:55 Debt-free engineering 10:36 The baggage we carry from the TDD era 12:53 Sebastian's kitchen: ZAR Core, a stablecoin wallet 14:53 The 37,000-line cleanup PR 16:22 Obie's kitchen: five Rails apps, 400k+ lines in five months 18:12 Nexus, Agentis, Imperium, Eventis 20:27 Delegation: --dangerously-skip-permissions and /goal 23:22 A kitchen that forgives: internal tools, don't panic 25:07 Same intolerance for debt, different timing 26:36 Rewriting the vibe-coded video app the Rails way 29:37 Compounding: 75 skills and counting 31:13 Skills tour: dev server, /fresh, /prod-exec, /ship 34:47 When the two kitchens collide 35:41 Flutter → React Native in two weeks 38:12 Scaling to a team: conventions constrain the model 42:02 Servus: a disciplined service-object pattern 44:24 Amounts: money math with type safety 45:38 Narrowing the path: Praxis and conceptual linting 48:30 Automated constraints will save us from ourselves 51:49 Eventis: an intelligent event mesh 54:03 What kind of kitchen works for your project? Links Obie Fernandez: https://obiefernandez.com Patterns of Application Development Using AI: https://leanpub.com/patterns-of-applicatio... RubyConf Austria: https://rubyconf.at RubyConf Austria 2026 took place May 29–31 in Vienna. Thanks to our speakers, sponsors, and community partners. #ruby #rails #ai #rubyconf #fintech